1. Field of the Invention
The present invention relates to a seat cushion for an automobile that provides a secure seat with a cozy feeling, increases driving comfort, and is particularly suitable for use as the front seat for the driver.
2. Prior Art
As a structure of such seat cushions used conventionally for vehicles, for example, there is one provided by the Japanese Utility Model Laid-Open Application No. 1982-351 (Title: Cushion Structure For A Seat). According to the foregoing Utility Model Application, it is "a structure of a seat cushion constructed by mounting a padding material formed into a specified shape, on a bottom plate, and by covering the said padding material with a facing sheet; in which the padding material is divided into two layers, that is, an upper layer and a lower layer, with the lower layer pad made harder than the upper layer pad, and a boundary plane between the upper layer pad and the lower layer pad formed into a shape fitting a body shape of a person who occupies the seat; also, a hardened layer is formed in the upper layer pad along its surface bordering on the lower layer pad."
The practical structure of the above is as mentioned below. That is, the upper layer pad obtained by placing a rigid fiber material, such as hair felt, on a bottom surface of a molding block for the upper layer pad, injecting foaming solution of polyurethane to thereby form the strong hardened layer with the foregoing rigid fiber material impregnated with polyurethane, along the underside of the upper layer pad, is superposed on the lower layer pad harder than the upper layer pad. The lower layer pad is obtained by foam-molding by using a separate mold. Then, the upper layer pad and the lower layer pad are wrapped with a facing sheet. Thereafter, they are fastened to the bottom plate, by appropriate means, such as hug rings. Also, for laying the upper layer pad on the lower layer pad, their boundary surfaces are formed into angled shapes at their front portions and rear portions in order to prevent the slipping off of the upper and lower layer pads from each other. In other words, the pads are not formed integrally, and the upper layer pad and the hard lower layer pad are formed by using respectively different molds, and then, they are overlapped on each other and fastened after covered with a trim cover.
Also, as a structure for the cushions for the front seat systems for drivers, for example, another is provided by the Japanese Utility Model Laid-Open Application No. 1983-58750 (Title: Driver Seat Structure Of Automobile). The description of this Utility Model Application is given as follows: That is, it is "a structure of a driver seat in an automobile, that is characterized in that, in a structure of the driver seat of automobile with a special form (differently formed) portion for relaxing provided at front area of the cushion seat, at least at the front area of the cushion seat, a right side portion and a left side portion of a seating portion are formed of elastic bodies which are different from each other in modulus of elasticity."
It means that, on the right side and the left side of the front area of the special form portion in the center area of the cushion seat, for giving relaxation, pads with qualities which are different from each other in terms of modulus of elasticity are buried along a front edge of the seating portion. Furthermore, the heights of the right and left side pads at the front edge portion of the cushion seat are made different from each other for the purpose of facilitating the conformity of the cushion of the front seat to the positional change of the thigh of the driver's leg, that is used for treading on the pedal.
"The Cushion Structure Of The Seat" provided by the prior art as mentioned above is a double layer structure in which the lower layer pad and the upper layer pad are formed by molding them separately, and the upper layer pad, with the hardened layer obtained by using a rigid fiber material formed along its boundary surface, is laid on a top of the separate lower layer pad; then, both of the foregoing pads are covered with a facing (trim) sheet and fastened. Therefore, it is defective in that it is inferior in stability of the cushion seat. In addition, because the front portion of the hardened layer is curved downward so that the height becomes reduced in the forward direction, it lacks stability suitable for sitting posture, and also it is inferior in providing good operability for the leg.
As to the "Driver Seat Structure Of Automobile," since the two types of pads made of the materials which are mutually different in modulus of elasticity are buried in the right and left side portions in the center area of the front portion of the cushion body, with which the thighs of the driver are in contact, an abrupt difference is caused in elasticity between the right and left sides in the boundary region in the center of the front area of the cushion body. Accordingly, not only is it difficult to obtain a comfortable sitting feeling because of the feeling of unfitness caused by the abrupt difference in elasticity, but also there is a defect that the front area of the cushion body always functions unevenly with respect to the height.